What type of wood door has a simple flat panel design without additional stopping mechanisms?

A slab door is characterized by its straightforward flat panel design, which means it lacks any additional elements or structural features such as grooves or decorative patterns found in more complex door styles. This simplicity makes slab doors versatile and easy to construct. They are often used in situations where a basic functional barrier is required without the need for ornate design or enhanced functionality.

The other door types offer different features; for instance, ledge doors typically have horizontal ledges that add structural support and are commonly used in barns. Panel doors consist of multiple panels framed by stiles and rails, giving them more visual interest and complexity. Rabbetted doors have a notch (or rabbet) on the edge, allowing them to overlap with the door frame for a more finished look and better sealing. These distinct characteristics set each door type apart, making the slab door the right answer for the question posed.